- Empire - A group of nations or peoples controlled by one sovereign nation.
- Good Neighbor Policy, the - Where America would step in to help another nation with their economy, and thus gaining control of it.
- Homestead Act of 1862, the - Distributed 160 acres of government land to people, who would be able to keep the land if they improved it within five years.
- Imperialism - The push for overseas expansion.
- Indian Wars - Fought between the U.S. and the Native Americans over Indian Territory. Ended in a Native American defeat.
- Land Ordinance of 1785 - One of the earliest means of creating boundaries.
- Louisiana Purchase, the - The acquisition of the Louisiana territory from Napoleon Bonaparte after he lost control of Haiti and failed to create a New World empire. It was meant to repay the French debt to America.
- Manifest Destiny - The American justification for their overwhelming expansion.
- Mexican-American War - Fought between Mexico and America. Ended in an American win, and allowed the U.S. to gain Mexico's territory.
- Open Door Policy, the - Declared that the U.S. had the right to advance its commercial interests anywhere in the world, at least on terms equal to those of the other imperialist nations.
- Overland Trails (1840s) - Trails crossing the North to California, Oregon, and the Mormon community in Utah.
- Santa Fe Trail (1821) - The first trail to encroach upon Indian territory.
- Seward's Icebox - The purchase of Alaska from Russia.
- Lewis and Clark Expedition (1804-06) - Exploration of the Louisiana territory.
- Transcontinental Railroad - A railroad expanding across America.
- Treaty of Guadalupe Hidalgo - Ended the Mexican-American War, and transferred the Mexican Territory to America.
- Treaty of Paris, the (1783) - Ended the Revolutionary War, and made the thirteen colonies into an independent country.
- Turner's Frontier Thesis - Stated that the Frontier had been vital in the growth and development of American culture.
- War of 1812 - The war that finally solidified American independence. It was fought against Britain, and successfully pushed Britain back, and contained them to Canada.
- The White Man's Burden - The idea that it was the duty of Americans to go to other countries and help them to convert to Christianity and develop a government.